Single acting hydraulic motor



Oct. 13, 19.59

J. L GRATZMULLER SINGLE ACTING HYDRAULIC MOTOR Filed May 7. 195s lllllllll GfaZamaZ/Zcp United States Patent Olice 2,908,251 Patented Oct. 13,` `1959 SINGLE ACTING HYDRAULIC MOTOR Jean Louis Gratzmuller, Paris, France Application May 7, 1956, Serial No. '583,284 Claims priority, application France May 13,1955 claims. (Crm1-4o) This invention relates to servo motor installations in, corporating a single-acting hydraulic motor, of the kind in which the hydraulic pressure is opposed by a permanent returning force, exerted for instance by a weight or resilient means, such as a spring.

The invention is more especially concerned with im stallations of this nature in which the operative stroke of the motor is the return stroke, the hydraulic pressure being used to extend the motor against the returning force and bring it into readiness for the return stroke which takes place when the motorisl exhausted. Such installations are adapted to the operation of the circuitbreakers.

If such a motor is maintained in readiness for actuation by the returning force solely by the hydraulic pressure, loss ofpressure, due for instance to leakage or failure of the pressure source, may lead to premature actuation, either complete or partial.

VAn object of the present invention is theprovision of means for automatically locking the motor on reaching its extended position of readiness for the return stroke, and for ensuring that the motor is unlocked substantially concurrently with or, more exactly, just before it is intentionally exhausted for the operative return stroke.

More particularly, it is an object of this invention to provide a locking member movable by a spring or like means to a position in which it engages and positively locks themovable member of the motor (hereafter referred to for better identification as the main motor) when said movable member reaches the extended position, said locking member being disengageable from said movable member to free the main motor by an auxiliary motor controlled by a primaryvalve which also controls the exhausting of the main motor.

A further object of the invention is to provide means for ensuring that the auxiliary motor cannot be prematurely actuated to free the main motor by leakage of liquid under pressure past the primary valve, said means including a drain communicating with a low-pressure region for receiving such leakage and means for blocking said drain when the primary valve is intentionally actuated to energise the auxiliary motor and exhaust the main motor.

Yet, another object of the invention is to provide means -ensuring that the main motor cannot be exhausted until it is freed by the action of the auxiliary motor, such means comprising secondary valve means controlling the exhausting of the main motor, said secondary valve means being operated by the auxiliary motor, after the latter has disengaged the locking member from the movable member of the main motor, to exhaust the main motor.

A still further object of the invention is to protect the mutually'engaging surfaces of the locking member of the movable member of the main motor against undue wear or eventual damage caused by excessive friction between them, by intcrposing between'the auxiliary motor ,and 4the locking member a resilient elort-limiting device.

How these objects are attained, together withjothers as may hereinafter appear, will'be more fully understood from the following description of two typical embodiments of the invention having reference to the accompanying drawings and given by way of example only, without implied limitation of the scope of the invention, which is defined in the hereto appended claims.

In'the drawings:

Fig. l is a schematic, partly sectional elevation of the iirst embodiment and j Fig. 2 is a schematic,` partly sectional view of `the second embodiment. v 4 g Referring to Fig. 1, the single-acting main motor com'- prises a cylinder 1 and a piston 2, which together with a piston rod 5 and a support 4 constitutes the movable member of the motor. Support 4 supports a Weight?, which provides the returningV force. Extension-of the movable member is limited by stops 7 which engage the piston 2. Rod 5 passes through an elongated slot 9 in a locking member or bolt 8 which can slide transversely of rod 5 in guides 10. When the movable member reaches the position of full extension, as shown inV the ligure, under the action of the hydraulic pressure of liquid sup- -plied to the working space of the motor below the ypiston from a source 31 through a control cock l6, the bolt8 registers with a square-section groove 11'in rod 5 and the part of bolt 8 at one end of slot 9 is automatically caused to enter groove 11 to retain the movable member 2, 5,- 4 in the extended position by the action of a compression spring 12,l which is interposed between the bolt 8 and a fixed abutment 13.

Bolt 8 is displaceable from this position to free the rod 5 and piston 2 by a single-acting auxiliary motor comprising a cylinder 16y and piston 15, whose rod 14 engages or is iixed to the end of bolt 8 remote from spring 1 2.

The working space of cylinder 1 communicates with that of cylinder 16 by a passage constituted by a pipe 19 a valve chamber formed in 'a housing 18 and a pipe 17. Housing 1-8 contains a primary valve constituted by a ball 20 and a seating 21.formed -in the chamber of housing 18. Ball 20 is removed from its seat by'a push rod 25 constituting an extension of the armature of an electromagnet 28, constituting a controllable means for actuating the valve. Excitation of magnet 28 displaces the armature and rod 25 (upwards in the figure) against the action of a loading spring 29, trapped between a collar 27 fixed to rod 25 and a lixed abutment at the base of housing 18, to unseat the ball 20. This puts the working space of cylinder 16 into communication with the source 31 of liquid under pressure through the passage 17, 18, 19 and the working space of cylinder 1, causing the piston 15 of the auxiliary motor to move (to the left in the figure) and displace the bolt 8 to free the rod 5 and piston 2. When, and only when, this has taken place, the piston 15 uncovers a port inv cylinder 16 whose working space is thereby put into communication with a drain pipe 24 leading to a sump 23. Piston 15 thus constitutes a secondary valve means which, when the main motor has been unlocked, enables its working space` to be exhausted to the sump through the passage 17, 18, 19, the working space of the auxiliary motor and pipe 24. p

Normally, the chamber of housing 18 below the seating 21 is in communication with the sump 23 through. a drain 22, which removes any liquid leaking past the ball 20 when seated. Such leakage Vcannot therefore build up pressure in the auxiliary motor and cause its premature actuation. When, however, the magnet 28 is excited to 'YIhe operation of the assembly may thus bek summarized as follows:

On applying hydraulic pressure to the main motor 1, 2 from source 31, the motor is extended against the returning force, of Weight 3. When fully extended, the motor is lockedautomatically by engagement of bolt'S with groove 11 under the action of spring 12. Loss of pressure in motor 1, 2 will therefore not cause the weight 3 to return the piston 2 and rod 5 to idle position, so that the pressure cock 6 may now be closed. When the motor 1, 2 is required to perform its operative return stroke under the action of weight 3, magnet 2S is excited by appropriate switch means (not shown) to unaccesar seat ball 20 andthereby apply pressure from source 31 to the auxiliary motor 16, which thereupon rst displacesbolt Sito free the main motor 1, 2, 5 vand then, by putting pipes 17 and 24 into mutual communication,

enables the hydraulic pressure in the main motor to be relieved through [passage 17, 18, 19 and pipe 24 and the operative return stroke of the main motor to be effected l by weight 3, the liquid in the main motor being exhausted through passage 17, 18, 19, cylinder 16' and pipe 24. Y

- The embodiment of Fig. 2 and its operation are generally similar to that of Fig. 1, corresponding parts being designated by the same reference characters. It is only necessary therefore to describe the respects in which this second embodiment differs from Ythe rst in structure and i function.

auxiliary motor piston 15 has `a head 32 which actuates the bolt 8 by displacing push rods 35, a telescopic assembly comprising a piston like disc 36 and a cylindrical casing 37, between which is trapped a compression spring 38,' and a push-rod 14 secured to casing 37. The telescopic assembly 36, 37, 38 constitutes an effort-limiting spring device, whose spring 38 is pre-loaded to a predetermined extent, the disc 36 being retained in the position shown in the figure by a shoulder formed on the inner surface 37 of the casing 37. This device 36-38 will Lprevent the auxiliary motor 16, 15 from releasing the `main motor piston and rod 2, 5 for the operative Vreturn stroke if excessive rfriction between the bolt 8 and the flanks of groove 11 is developed, in which case repeated forciblediseng'agement of the bolt 8 from groove 11 would cause excessive wear of, and eventual serious damageto, the interengaging surfaces of bolt 8 and rodv 5. Such excessive friction can result from slight leakage in the main motor 1, 2 causing a loss of pressure therein which, while insuficient to make the auxiliary motor inoperative, may significantly increase the bearing working space is directly connected with the above mentioned separate chamber by a'pipe 19a of larger diameter than and branched from pipe 19 between the main motor and the primary valve 18, 20. Ball 34 is unseatable by a push rod 33 fixed to head 32, and lying in bore 16C communicating with the chamber and cavity 16ay butv `only after the latter has been displaced suiciently to disengage the bolt 8 from the groove 11 of the main motor piston rod 5. n When ball 34 is unseated, pipe 19a is put into communication, via a cavity 16a in the cylinder 16, with a drain 24a leading to sump 23. Y

In this arrangement therefore, the main motor 1, 2 is exhausted to the sump 23 via pipe 19a, the above mentioned separate ball chamber and cavity,l and pipe 24a,

parts and/or mechanisms as 'may be within the cornn petence of kthose skilled in the art and are comprised within the scope of the hereto appendedV claims.

Whatisclaimed is: l

1. In combination` with a main single-acting hydraulic motor comprising a fixed member, a movable member, means for applying uid under pressure to the motor to move said movable member to an extendedposition and means constantly applying a force to said movable member in a direction tending to return it to a retracted position, a locking member directly cooperable with said Vmovable member and displaceable `between an operative position and an inoperative position and adapted when in the operative position to directly engage and positively lock said movable member when the latter is in the extended position, means constantly applying a force on said locking member in adirection urging it to operative .position, an auxiliary single-acting hydraulic motor operative on the admission thereto of uid under ypressure n venting exhaust of the main motor, discharge passage means controlled by said auxiliary' motor for exhausting said main motor, and controllable means Vfor opening said `valve means to admit hydraulic .pressure from the main motor to the auxiliar-y motor to thereby allow the main vmotor to be exhausted when the lockingmember has been displaced to inoperative position.

2. In combination with a main single-acting hydraulic motor comprising a fixed member, a movable member, means for applying uid under pressure to the motor to move said movable member to an extended position andV means constantly applying a force to said movable member in a direction tending to return it to a retracted position, a locking member directly cooperable with said movable member displaceable between an operative position and an inoperative position and adapted when in the operativeYV position to directly engage and positively lock said movable member when the latter is in the extended position, means Vconstantly applying a force kon said locking member in a direction urging it to operative position, an auxiliary single-acting hydraulic motor operative on the admission theretoof liuid under pressure to move the locking member to inoperative position, a Vpassage means interconnectingthe main and auxiliary motors, a primary valve meansV normally closing lsaid passage means, controllable means for opening said primary valve means to admit fluid lunder pressure from the main motor to the auxiliary motor, and secondary valve means actuated by the auxiliary motor for exhausting the main motor when and not until the auxiliary motor has moved thelockin'g member to inoperative position.

3. In combination with a main single-acting hydraulic motor comprising a lixed member, ay movable member, means for applying uid under pressure to the motor to move'said movable member to an extended position and means constantly applying a force toV said movable member in a direction tending to return it'to a retracted position, a locking member directly cooperable with the and not through'the working space of cylinder 16. The 75 `lock said vmovable `member when the latter is in the extendedfposition, means constantly applying a ,force on said locking member in a direction urging it to operative position, an auxiliary single-acting hydraulic motor comprising a fixed cylinder and a movable piston operativeqon the admission ofrhydraulic pressure to said cylinder to move the locking member to inoperative position, a passage interconnecting said cylinder` with the main motor, a primary valve normally closing said passage, controllable means for opening saidprimary valve tofadmitrliquid under pressure from the main motor to said cylinder, a port in said cylinder and a drain connected thereto, said port being placed so as to be uncovered by said piston to allow the main motor to be exhausted through` said passage and said cylinder when the said piston has moved the locking member toinoperative position. 4. In combination with a main single-acting hydraulic motor-comprising a fixedA member, a movable member, means for applying uid under pressure to the motor to move said movable member to an extended position andv means yapplying a steady force to said movable member tending to return it to a retracted position, a locking member directly cooperable with said movable member and displaceable between an operative position and an inoperative position and adapted when in the operative position to directly engage and positively lock said movable member when the latter is in the extended position, means constantly applying a force on said locking member in a direction urging it to operative position, an auxiliary single-acting hydraulic motor operative on the admission thereto of fluid under pressure to move the locking member to inoperative position, a passage interconnecting the main and auxiliary motors, a primary valve normally closing said passage, controllable means for opening said primary valve to admit liquid under pressure from the main motor to the auxiliary motor, a chamber, a passage interconnecting the main motor and said chamber, an opening in said chamber constituting a ball-seating, a ball normally seated thereon, a drain communicating with said opening, and a member actuated by the auxiliary motor and adapted, when the auxiliary motor has moved'the locking member to inoperative position, to unseat said ball and thereby allow the main motor to be exhausted through said second-named passage, said chamber and said drain. 5. In combination with a main single-acting hydraulic motor comprising a xed member, a movable member, means for applying fluid under pressure to the motor to move said movable member to an extended position and means constantly applying a force to said movable member in a direction tending to return it to a retracted position, a locking member directly cooperable with the movable memberand displaceable between an operative position and an inoperative position and adapted when in operative position to directly engage and positively lock said movable member when the latter is in the extended position, means constantly applying a force on said locking member in a direction urging it to operative position, an `auxiliary single-acting hydraulic motor operative on the admission thereto of liuid under pressure to move the locking member to inoperative position, normally closed valve means preventing the admission of fluid under pressure to the auxiliary motor, said valve means also preventing exhaust of the main motor, discharge passage means for exhausting said main motor, controllable means for opening said valve to admit hydraulic pressure to the auxiliary motor and to allow the main motor to be exhausted, a drain adapted to receive leakage past said valve when closed, and other valve means actuated by said controllable means for blocking said drain when said first-named valve is opened. 6. In combination with a main single-acting hydraulic motor comprising a xed member, a movable member, means for applying iluid under pressure to the motor to move said movable member to an'extended position and means constantly applying a force to said movable member in a directionrtending` to return it to a retracted position, a locking member directly cooperable with said movable member and displaceable between an operative position and an .inoperative position and adapted when in the operative position to directly engage and positively lock saidmovable member when the latter is in the extended position, means constantly applying a force on said locking -member in a direction urging it to operative position, an auxiliary single-acting `hydraulic motor operative on the admission thereto of fluid under pressure to move thelocking member toinoperative position, a valve comprising a .ball-seating and a ball normally seated thereon to prevent the admission of hydraulicv pressure to the auxiliary motor and the exhausting of the main motor, discharge passage means for exhausting the main motor, a push rod adapted to unseat said ball, and controllable means for actuating said push rod'to unseat said ball and thereby to admit hydraulic pressure to the auxiliary motor and to allow the main motor to be exhausted when the locking member has been displaced to inoperative position.

7. In combination with a main single-acting hydraulic motor comprising a xed member, a movable member, means for applying fluid under pressure to the motor to move said movable member to an extended position and means constantly applying a force to said movable member in a direction tending to return it to a retracted position, a locking member directly cooperable with said movable member and displaceable between an operative position and an inoperative position and adapted when in the operative position to directly engage and positively lock said vmovable member when the latter is in the extended position, means constantly applying a force on said locking member in a direction urging it to operative position, an auxiliary single-acting hydraulic motor operative on the admission thereto of iluid under pressure to move the locking member to inoperative position, a valve comprising a ball-seating and a ball normally seated thereon to prevent the admission of hydraulic pressure to the auxiliary motor and the exhausting of the main motor, discharge passage means for exhausting the main motor, a push rod adapted to unseat said ball, a drain adapted to receive leakage past said ball when seated, a member mounted on said push rod and adapted, when said push rod is moved to unseat said ball, to block said drain, and controllable means for actuating said push rod to block said drain and to unseat said ball and thereby to admit hydraulic pressure to the auxiliary motor and to allow the main motor to be exhausted when the locking member has been displaced to inoperative position.

8. In combination with a main single-acting hydraulic motor comprising a iixed member, a movable member, means for constantly applying iluid under pressure to the motor to move said movable member to an extended position and means constantly applying a force Ato said movable member in a direction tending rto return it to a retracted position, a locking member directly cooperable with said movable member and displaceable between an operative position and an inoperative position and adapted when in the operative positionto directly engage and positively lock said movable member when the latter is in the extended position, means constantly applying a force on said locking member in a direction urging it to operative position, an auxiliary single-acting hydraulic motor operative on the admission thereto of iluid under pressure to move the locking member to inoperative position, a normally closed valve preventing the admission of pressure to the auxiliary motor and the exhausting of the main motor, discharge passage means for exhausting the main motor, and controllable means comprising an electromagnet for opening said valve to admit uid under pressure to the auxiliary motor and to allow the main motor to be exhausted when theflockingv member has been displaced' to inoperative position.

9; In combination witha main Vsingle-acting hydraulic motor-comprising ,a fixed'member, amovabl'e member', means for constantly applying iluid under pressure to the motor to move said vmovable member to an extended position and'means constantly applying a force to said movable member in a direction tending torreturn it torretracted position, a locking member directly cooperable with said movable member and displaceable between an perative position Vand an inoperative position and adapted when in the operative position to directly engage and positively lock said movable member when the latter is in the extended position, means constantly applying a force on rsaid locking member'in a direction urging it to operative position ari-'auxiliary single-acting 'hydraulic motor operative on the admission thereto of fluid under pressure to move the locking member to inoperativepo- Vsition, eiort-Vlimiting" resilient means interposed between fthe auxiliary `motor and the locking member, normally closed valve means preventing the admission of fluid under pressure to the auxiliary motor and the exhausting of the main motor, discharge passage means for 4exhausting the main motor, and controllable means forV opening said valve to admit hydraulic pressure to the auxiliaryv mo'- .torlandto allowtlie mainimojtortobe exhausted when the locking memberl has. been displaced` `toy inoperative position. i

-lOfThecombination defined Yin claim9`J `in;whic'iltiie eiort-limiting resilientvmeans comprises ja iirs't member displaceableby the auxiliary motor, a second member ,telescopically'slidable on` said irst member, 'a compression springY trapped between said rst, andsecond'memf bers, andV a locking member-actuating pushrod `mounted on said second member. L

i Y, References Cited in the le of this patent 

